1. Field of the Invention
This invention relates to a semiconductor for electronics and a semiconductor device using the semiconductor. More particularly, this invention relates to Group III-V compound semiconductor that will be suitable for a novel and excellent optical semiconductor, and a semiconductor device.
2. Description of the Related Art
Recently, a blue-color light emitting diode using InGaN of Group III-V compound semiconductor has been put into practical use, and blue-color laser oscillation has come close to a practical level. Such Group III-V compound semiconductor is fabricated on a substrate by crystal growth under a high temperature condition of 800 to 1,100xc2x0 C. by chemical vapor phase deposition of an organometallic compound (MOCVD).
A sapphire substrate or a silicon carbide substrate is generally used as the substrate on which the Group III-V compound semiconductor is grown. Though transparent, the sapphire substrate is an insulating substrate. The size of the sapphire substrate is limited, and its cost is high. The silicon carbide substrate is electrically conductive but is more expensive than the sapphire substrate. Its size, too, is limited much more than the sapphire substrate. The crystal growth of the Group III-V compound semiconductor on these substrates is made using a buffer layer of GaN or AlN.
In comparison with silicon materials that account for the major proportion of present semiconductor devices and products, the Group III-V compound semiconductor has a great difference of the lattice constant and cannot provide a quality film. Therefore, crystal growth is made using an SiC buffer layer, or the AlN or GaN low temperature growth buffer layer employed for the sapphire substrate. Nonetheless, satisfactory quality cannot yet be acquired.
Great effects will be obtained in both aspects of performance and cost in hybridization of an electronic device using a silicon semiconductor and an optical semiconductor using Group III-V compound semiconductor if the Group III-V group semiconductor can be directly formed on a silicon material.
As described above, however, the conventional Group III-V compound semiconductor is fabricated generally by the chemical vapor phase deposition of an organometallic compound at a high temperature of 800 to 1,100xc2x0 C. Therefore, film quality is affected greatly not only by the difference of the lattice constants but also by the difference of thermal expansion coefficients.
When the film is formed on the substrate having a great difference in both lattice constant and thermal expansion coefficient such as a silicon material, the influences of these factors must be taken into account and the low temperature growth is preferably carried out.
Hydrogenated amorphous silicon or microcrystal silicon material is suitable for the substrate of two-dimensional devices having a relatively large area. According to the prior art technologies using the high temperature, however, constituent elements and addition elements fall off at the time of heating of the substrate, and the Group III-V compound semiconductor cannot be fabricated on such a substrate.
A greater area and a lower cost of production could be achieved in display devices and optical photo-electromotive devices if a glass substrate could be used as a transparent substrate. However, the prior art methods cannot fabricate the Group III-V compound semiconductor due to the limit of the heat resistance of glass.
The temperature that can be employed for these various substrates is determined primarily by the occurrence of crack and peel that result from the difference of the thermal expansion coefficients between the substrate and the film to be formed, heat resistance of the substrate itself (such as softening point, crystallization point, fall-off of constituent elements and addition elements), and so forth. For instance, if hydrogenation is made in a post-treatment in not only a hydrogenated amorphous silicon but also mycrocrystalline silicon, substrate performance cannot be secured at a temperature of 600xc2x0 C. or above if any element is added.
A low temperature film forming method makes it possible to directly form a film on these substrates on which the film formation has been difficult in the past. For this reason, Group III-V compound semiconductor that can be formed at a low temperature has been eagerly required.
Therefore, the inventors of the present invention have proposed a method that uses remote plasma as the low-temperature film forming method. Though the Group III-V compound semiconductor film formed by such a film forming method can provide film characteristics such as photo-electric conductivity, further improvements are yet to be made because sensitivity and response are not sufficient for use in optical semiconductor devices.
It has been reported in the past that in the Group III-V compound semiconductors fabricated at 800 to 1,100xc2x0 C. by the conventional vapor phase deveoposition method of the organometallic compound, a p type dopant combines with a trace amount of hydrogen atoms and hinders activation of the dopant, and annealing at 400xc2x0 C. or above, preferably at 600xc2x0 C. or above, in a nitrogen atmosphere is therefore necessary. When low-temperature film formation is conducted, an additive, an adding method, a film-forming method, etc., that do not call for such an annealing treatment, are necessary for the low-temperature film formation.
Though intensive studies have been made on such Group III-V compound semiconductors, further improvements must be yet made.
Solar cells have been utilized vigorously in recent years. To use them in all places, the solar cells are used preferably in the form that is free from limitation as much as possible. Nonetheless, the conventional solar cells involve the problems in design such as colors, and have therefore been used in only limited places.
In view of the problems with the prior art technologies described above, the present invention is directed to improve the drawbacks of the Group III-V compound semiconductors.
According to one aspect of the present invention, there are provided an economical Group III-V compound semiconductor free from the limitation of shape and size, and a semiconductor device using the compound semiconductor.
According to another aspect of the present invention, there are provided Group III-V compound semiconductor excellent in photo-electric characteristics (photo-electric conductivity, photo-electromotive force, quantum efficiency), and a semiconductor device using the compound semiconductor.
According to still another aspect of the present invention, there are provided Group III-V compound semiconductor that makes it possible to freely select an optical gap over a broad range, has only a limited change with time, and is excellent in response, environmental resistance characteristics and high-temperature resistance, and a semiconductor device using the compound semiconductor.
The inventors of the present invention have conducted intensive studies on the drawbacks of the conventional Group III-V compound semiconductors described above, and have completed the present invention. The gist of the present invention resides in the following points.
 less than 1 greater than  A group III-V compound semiconductor containing principally a Group III element and a Group V element of the Periodic Table, and containing 0.1 to 40 atom % of hydrogen atoms and 100 ppm to 20 atom %, based on the sum of the atomic numbers of the Group III element and the Group V element, of at least one element selected from among Be, Mg, Ca, Zn and Sr.
 less than 2 greater than  A Group III-V compound semiconductor according to the item  less than 1 greater than , that contains 2,500 ppm to 15 atom %, based on the sum of the atomic numbers of the Group III element and the Group V element, of at least one element selected from among Be, Mg, Ca, Zn and Sr.
 less than 3 greater than  A Group III-V compound semiconductor according to the item  less than 1 greater than  or  less than 2 greater than , that is a non-single crystal compound.
 less than 4 greater than  A Group III-V compound semiconductor according to any of the items  less than 1 greater than  through  less than 3 greater than , that has a columnar structure.
 less than 5 greater than  A Group III-V compound semiconductor according to any of the items  less than 1 greater than  through  less than 4 greater than , wherein each of Ia/Ic and Ib/Ic is not greater than 0.5 where Ia is absorbance of an infrared absorption peak based on bonding between the Group V element and the hydrogen atom, Ib is absorbance of an infrared absorption peak based on bonding between the Group III element and the hydrogen atom, and Ic is absorbance of an infrared absorption peak based on bonding between the Group III element and the Group V element.
 less than 6 greater than  A Group III-V compound semiconductor according to any of the items  less than 1 greater than  through  less than 5 greater than , wherein an absorption coefficient (absorbance/film thickness) of the infrared absorption peak based on bonding between the Group V element and the hydrogen atom and an absorption coefficient (absorbance/film thickness) of the infrared absorption peak based on bonding between the Group III element and the hydrogen atom are 5 cmxe2x88x921 to 5,000 cmxe2x88x921, respectively.
 less than 7 greater than  A semiconductor device including a layer formed of the Group III-V compound semiconductor according to any of the items  less than 1 greater than  through  less than 6 greater than  and a second electrode disposed on a first electrode.
 less than 8 greater than  A semiconductor device according to the item  less than 7 greater than  which is an photo-electromotive device or a light reception device.
 less than 9 greater than  A semiconductor device according to the item  less than 7 greater than  which bears the two functions of an photo-electromotive device and a light reception device.
The film of the Group III-V compound semiconductor according to the present invention can be formed at a low temperature. Therefore, it can be formed on a free substrate at a low cost of production without the limitation of its shape and size.
The Group III-V compound semiconductor according to the present invention is excellent in photo-electric characteristics when it contains a specific amount of at least one member selected from among Be, Mg, Ca, Zn and Sr.
The Group III-V compound semiconductor according to the present invention can freely select an optical gap over a broad range depending on its composition, has high performance as an optical semiconductor and a limited change with time, and is excellent in response, environmental resistance characteristics and high temperature resistance.